The present invention relates to a wet brake system for braking the motion of a rotating component or device such as, for example, a wheel of a vehicle or a winch of a crane.
Wet brake systems and components thereof are described in Applicant""s International application Numbers PCT/AU92/00540, PCT/AU95/00529 and PCT/AU97/00500, the contents of which are incorporated herein by way of reference.
In broad terms, a wet brake system typically includes a disc fixed to rotate with a rotating component, a pair of brake pads disposed on opposite sides of the disc and a sealed housing containing the discs and the brake pads. The housing contains a volume of oil trough which the disc rotates. An equivalent dry brake system includes a disc and brake pads similar to the wet brake system but does not include an oil containing housing in which the disc and brake pads reside.
Benefits of a wet brake system over a dry brake system include a substantially reduced rate of wear of the brake pads and, because of the sealed housing, the ability to isolate contacting the surface of the disc and pads from foreign matter and debris that may otherwise adversely affect the performance or increase the rate of wear. Nevertheless, a substantial disadvantage of the wet brake system is that it has substantially reduced stopping power in comparison to a dry brake system having comparable brake pad area. This arises because of the presence of the oil in the housing which acts to reduce friction between the brake pads and discs.
The present invention was developed with a view to providing a wet brake system with improved stopping power.
According to the present invention there is provided a brake system for a rotating component, said brake system including at least:
a plurality of discs coupled to said component to rotate with said component about an axis, each disc having first and second opposite radial surfaces;
a plurality of brake means fixed against rotation but linearly movable relative to said discs parallel to said axis, each brake means having a braking surface;
said discs and brake means juxtaposed so that at least one of the radial surfaces of each disc is facing the braking surface of a braking means;
at least one of the facing braking surface aid the radial surface is provided with a plurality of grooves, said grooves orientated to provide fluid flow paths across said at least one of said facing braking surface and radial surface;
means for axially moving said braking means relative to said disc between an engaged position where said braking surface is in engagement with a facing radial surface and a disengaged position where said braking surface is spaced from said facing radial surface; and
a sealed housing in which said discs and braking means reside, said housing containing a volume of liquid through which said discs rotate.
Preferably, said braking surface is provided in a plurality of spaced apart sectors, each sector having an inner circumferential face, an outer circumferential face and opposite first and second radial faces extending between said inner circumferential face and said outer circumferential face.
Preferably, said grooves are formed on the braking means and include one or more grooves that extend from the first radial face to the outer circumferential face of each sector.
Preferably, said grooves include one or more grooves that extend from the inner circumferential face to the outer circumferential face of each sector.
Preferably, said grooves include one or more grooves that extend from the inner circumferential face to the second radial face of each sector.
Preferably, there are four sectors, said sectors spaced evenly about said braking means wherein each sector extends for an arc angle of at least 45xc2x0.
Preferably, said braking spice extends over a cumulative arc angle of at least 180xc2x0 about said brake means.
Preferably, said braking means is in the form of a brake disc and said braking surfaces are radial exposed surfaces of brake pads supported by said brake disc.
Preferably, said plurality of grooves include a plurality of grooves formed on each radial contacting surface facing a braking surface.
Preferably, each radial contacting surface facing a braking means is provided with a raised annular band having an inner circumferential edge and an outer circumferential edge and wherein the grooves on said radial contacting surface extend from the inner circumferential edge to the outer circumferential edge of the annular band.
Preferably, said brake system further includes at least one scraping means supported on at least one of said braking means for scraping liquid from a facing radial surface of a disc, said scraping means axially moveable between a first position in which said scraping means extends axially beyond the braking surface of said at least one braking means and a second position where said scraping means is retracted axially to lie substantially flush with or below said braking surface whereby when said braking means is moved toward said engaged position said scraping means engages said facing radial surface prior to said braking surface engaging said facing radial surface.
Preferably, said braking system further includes first bias means for biasing said scraping means toward said first position.
Preferably, said scraping means includes a contact face for contact with said facing radial surface, said contact face provided with one or more scraper grooves configured to provide one or more fluid communication paths across said contact face.
Preferably, a scraping means is provided between at least one set of mutually adjacent sectors. respectively.